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UNITED STATES PATENT @rrioa.

DAVID. N. OARVALHO, OF NEW YORK, N. Y., ASSIGNOR OF ONEHALF TO ERNEST MARX, OF SAME PLACE.

METHOD OF PRODUCING PHOTOGRAPHIC IMAGES.

SPECIFICATION forming part of Letters Patent No. 234,171, dated November 9, 1880.

Application filed April 8, 1880. (Specimens) plate then exposed in the camera to the action of the light. It is then taken into the dark room and developed, and finally fixed or cleared up with cyanide of potassium or hyposulphite of soda, the resulting picture being a negative or positive, according to the sup port used for the substratum. The main objection to this process is the use of the fixing agents, as cyanide of potassium is one of the most virulent poisons, the fumes of which are deleterious to health, and as hyposulphite of soda, though not objectionable in this respect, forms, like cyanide of potassium, an element of destruction to the picture.

The object of my invention is to dispense entirely with afixing agent in the ordinary silver process, so as not only to simplify and accelerate the production of the image, but also to dispense with the printing of the positives.

The invention consists in impart-ing to the substratum a dense color, exposing it to the action of the light in the camera and developing it upon the colored ground, but without fixing, so as to obtain apositive picture by simple exposure and development.

The substratum, such as collodion, albumen, gelatine, glue, or any other suitable substance, is mixed in excess with a dense heavy color, which forms, so to say, the background for the picture. The substratum is placed on any suitable support. of glass, metal, paper, or other material. The substratum is sensitized and then exposed in the camera to the The plate is then developed, with this difference, however, that the manipulator has to observe the gradual appearance of the high lights until a complete positive image is obtained on the background of dense color, instead of following the rule that when the shadows commence to disappear developing has to stop.

In place of anegative, as heretofore, apositive is worked out, which stands out in bold and clear relief from the colored ground. No fixing in the dark room is thereby required, and the result is a new type of photographic picture. The dense color forming the background causes the image to appear as a positive picture, and thus shortens and simplifies the ordinary collodiou-silver process, as it admits the delivery of the pictures directly after the sitting, dispensing with fixing and printing.

Having thus described my invention, I claim as new and desire to secure by Letters Patent 1. As an improvement in the art of producing that class of photographic pictures in which nitrate of silver is employed as the sensitive agent,the process hereiubet'ore described, which consists, essentially, in the followingnamed steps: first, providing the substratum or picture-supportiug film with a tint or color of sufticient depth and opacity to intercept the rays of light and form the background for a positive picture; second, sensitizing said support by immersion in a nitrate-ot-silver bath; third, exposing the samein the camera; and, finally, subjecting it to the action of a developing agent until the image becomes distinctly visible, and thus complete the picture, whereby the use of any fixing agent is en tirely dispensed with, substantially as described.

2. A photographic picture composed of a substratum or support provided with a color of sufiicient density and opacity to intercept the passage of light, a surface rendered scusitive to light by means of a nit-rate-of-silver deposit, and a surface deposit of iron or other suitable ingredient for developing the image and completing the picture, substantially as described, and for the purpose set forth.

DAVID NUNES OARVALHO.

Witnesses H. A. KNowLns, PHILIP HOUSTON. 

